Motor vehicle front end comprising a bumper unit

ABSTRACT

The invention relates to a front part of a motor vehicle having a fender unit which comprises a front fender which is covered on the outside by a fender covering, and which is connected in its lower region to a bottom supporting structure of the motor vehicle, an air guiding part being arranged underneath the fender.  
     According to the invention, in the event of a head-on impact the air guiding part interacts with the fender covering and stiffens it in a region which is positioned in front of the fender, the air guiding part being supported on the bottom supporting structure.

[0001] The invention relates to a front part of a motor vehicle having afender unit according to the preamble of patent claim 1.

[0002] DE 38 25 071 C1 has already disclosed a front part of a motorvehicle with a fender unit which is connected to a bottom supportingstructure of the motor vehicle and in which cooling air openings aremade in a fender covering in order to supply cooling air to the driveassemblies arranged behind the fender unit. The cooling air openings arearranged above and below a transverse carrier which is associated withthe fender unit and into which a fender which is elastic with respect toimpacts is integrated.

[0003] In order to pass on the air flowing through the cooling airopenings to the drive assemblies with as few flow losses as possible, anair guiding part, which forms an air guiding duct, is arranged betweenthe fender covering and the bottom supporting structure.

[0004] With such or similar additional assemblies for improving theefficiency of the drive assemblies in the front region of a motorvehicle, the packing density is increased more and more so that there isless structural free space for the configuration of measures to improvepedestrian protection in the event of collisions.

[0005] The invention is therefore based on the object of developing afront part of a motor vehicle of the generic type to the effect that,while maintaining the advantageous effect of the air guiding part,protection of pedestrians in the event of a collision is improved.

[0006] This object is achieved according to the invention by means ofthe features of patent claim 1.

[0007] Advantageous refinements of the invention can be found in theother claims.

[0008] By reinforcing the fender covering with a component which isalready present, such as the air guiding part, the structural spacewhich is available in the front of the motor vehicle for improving theimpact protection for pedestrians is utilized to an optimum degree.Here, the air guiding part has a reinforcing effect on the fendercovering in a region positioned in front of the fender so that in theevent of a collision a pedestrian firstly enters into contact with thisregion which runs approximately at the level of the pedestrian's lowerlegs. The movement impetus which acts in the lower leg region away fromthe front part of the motor vehicle causes the pedestrian to be slungaround about the center of gravity of his body so that his upper bodymoves in the direction of the engine hood. In the process, the fenderwhich is of resilient construction is pressed in so that the pedestrianrolls across the engine hood in a defined fashion. At the same time, thereinforcement of the fender covering acts as an under-ride protectionfor pedestrians so that they cannot be pulled under the motor vehicle inthe event of a collision. The air guiding part is set here in such a waythat the necessary supporting force is reached quickly and maintainedwhile the acceleration values and the necessary penetration paths forthe pedestrian are preserved.

[0009] As the air guiding part extends over virtually the entire widthof a motor vehicle, the fender covering is also reinforced in thelateral regions of the front part of the motor vehicle, and at the sametime the cross-sectional surface which is available in the front area ofthe motor vehicle is used to an optimum degree for feeding cooling air.

[0010] In one preferred embodiment, the air guiding part is supported atthe front end by two longitudinal carrier sections which are associatedwith the bottom supporting structure. The air guiding part is embodiedas an injection-molded part, and the plastic used should be relativelyrigid, impact-resistant and not too brittle. The connection to the frontends of the longitudinal carrier sections permits stable support onalready existing components which can be integrated into theinjection-molded part without much additional expenditure on change.

[0011] A rear end collision protection element which is fitted over thefront ends of the longitudinal carrier sections acts, in addition to itsfunction as a support of the air guiding part, as a rear end collisionprotection in the event of minor damage. For example, when the rear endof the motor vehicle strikes against curves or the like, thelongitudinal carrier sections which are associated with the supportingstructure can be protected to an optimum degree against damage by therear end collision protection element. The rear end collision protectionelement is preferably manufactured from plastic so that adaptation tovirtually any shape of the connection between the supporting structureand the air guiding part can be brought about.

[0012] In order to reduce the manufacturing costs further, the airguiding part can be constructed as one piece with the rear end collisionprotection element.

[0013] As a result of the air guiding part extending laterally beyondthe supporting points on the front ends of the longitudinal carriersections, the pedestrian protection is also provided even when there isan offset collision with a pedestrian.

[0014] In order to support the air guiding part uniformly on the fendercovering, the contour of the air guiding part which faces the fendercovering is adapted to the internal contour of the fender covering. Inaddition, the fender covering can be prestressed by the air guiding partin order to improve the dimensional stability of the fender covering.

[0015] In one particularly preferred embodiment, the air guiding parthas a wing-like shape. In order to make the air guiding part inherentlystable, a number of reinforcement ribs which are oriented in thelongitudinal direction of the motor vehicle and which are spaced apartfrom one another in the transverse direction of the motor vehicle arearranged on the upper side of the wing.

[0016] Reinforcement ribs which extend from the underside of the wing inthe direction of the fender covering act in a particularly reinforcingfashion in the lower region of the fender covering. The matching of theterminating edge of each reinforcement rib to the internal contour ofthe fender covering particularly increases the degree of rigidity inthis region so that in the event of a crash the lower limb of apedestrian can bounce off.

[0017] The formation of an at least partially closed hollow section bythe covering the fender and the air guiding part provides furtherreinforcement in order to protect pedestrians against impacts withsimple means. Here, the wing can be attached by its terminating edges tothe fender covering, or else only bear against it.

[0018] In addition to supporting the air guiding part on both sides onthe front ends of the longitudinal carrier sections it is possible toprovide support on a transverse carrier which connects the frontlongitudinal carrier sections. This further improves the degree ofrigidity of the fender covering in the lower region.

[0019] Further advantageous refinements of the invention are explainedbelow with reference to the drawing, in which:

[0020]FIG. 1 shows a longitudinal sectional view at the level of aright-hand longitudinal carrier of a front part of a motor vehicle,

[0021]FIG. 2 shows a longitudinal sectional view at the level of themotor vehicle center of the front part of a motor vehicle,

[0022]FIG. 3 shows a plan view of the air guiding part which isillustrated in FIGS. 1 and 2,

[0023]FIG. 4 shows a longitudinal sectional view at the level of themotor vehicle center of a front part of a motor vehicle in a secondembodiment,

[0024]FIG. 5 shows a perspective oblique view of an air guiding part ina third embodiment, and

[0025]FIG. 6 shows a perspective view of the arrangement of the airguiding part according to FIG. 5 in the fender unit in a perspectiveoblique view from behind.

[0026]FIG. 1 illustrates a front part 1 of a motor vehicle having afender unit 2 in a longitudinal section which runs at the level of afront longitudinal carrier section 3, the longitudinal carrier section 3being associated with a bottom supporting structure (not illustrated inmore detail) of a motor vehicle.

[0027] The fender unit 2 comprises a front fender 4 and a fendercovering 5.

[0028] The front fender 4 is formed by a transverse carrier 6 which isconnected to a supporting component 8 of the motor vehicle by means ofan impact absorber 7. An impact foamed part 10, which extends overvirtually the entire width of the motor vehicle, is attached to thefront end side 9 of the transverse carrier 6 which is embodied as atwo-chamber hollow section. The impact foamed part 10 has a U-shapedcross section.

[0029] The front part 1 of the motor vehicle is terminated at the frontby the fender covering 5 which is connected in the upper region to amotor vehicle bodywork frame part 11 and a side part 12 by means of ascrewed connection 13. A cooling air opening 14 which extends at leastpartially over the width of the motor vehicle is made in the fendercovering 5 below the front fender 4 in order to supply sufficientcooling air to the drive assemblies arranged in the engine cavity 15. Inthis exemplary embodiment, the cooling air opening 14 is configured tosupply cooling air to a charge air cooler which is however notillustrated in FIG. 1.

[0030] An air guiding part 16 which is attached by means of a rear endcollision protection element 17 to the front end 18 of the longitudinalcarrier section 3 is arranged underneath the cooling air opening 14. Forthis purpose, the rear end collision protection element 17 isconstructed as a single plastic component together with the air guidingpart 16, the rear end collision protection element 17 being attached inits rear region 19 to the longitudinal carrier section 3 by means of ascrewed connection 20. The rear end collision protection element 17 isshaped in such a way that its internal contour is essentially matched tothe external contour of the front end 18 of the longitudinal carriersection so that the rear end collision protection element 17 can easilybe fitted over the front end 18. At the same time, the lower lip 21,extending underneath the cooling air opening 14, of the fender covering5 is attached by means of a screwed connection 22 to the rear endcollision protection element 17 and thus to the front longitudinalcarrier section 3.

[0031] The air guiding part 16 extends in a wing shape over virtuallythe entire width of the motor vehicle, irrespective of whether or not acooling air opening 14 is arranged above. With its terminating edge 23which faces the fender covering 5, the air guiding part 16 which extendsin a tongue shape in the longitudinal direction of the motor vehiclebears against the inner contour 24 of the fender covering 5, the innercontour 24 being formed in the abutment area of the terminating edge 23as an engagement angle 25 in order to support the air guiding part 16 ina way which is low in vibration. In order to reinforce the air guidingpart 16, reinforcement ribs 26 which are oriented in the longitudinaldirection of the motor vehicle are arranged on the upper side of saidair guiding part 16. Depending on the desired degree of rigidity, thenumber of reinforcement ribs 26 can be increased in the transversedirection of the motor vehicle, the distances between the reinforcementribs 26 being correspondingly reduced.

[0032] Covering the lower lip 26 with the air guiding part 16 results inan air guiding duct 27 which is closed at least in the downwarddirection and through which the air which flows in is directed to thecharge air cooler in a selected fashion. The tongue-shaped configurationof the air guiding part makes it possible to ensure that the air whichhas flowed in is used to an optimum degree without undesired flow lossesoccurring. At the same time, adaptation to the structural conditions inthe front area of the vehicle occurs, the air stream which entersthrough the cooling air opening 14 being capable of being oriented in aselected fashion with respect to the drive assembly which is to becooled.

[0033] When there is a pedestrian collision, the air guiding part 16acts in a reinforcing fashion on the lower lip 21 which is associatedwith the fender covering 5 and is positioned slightly in front of thefender 4. The lower lip 21 is correspondingly the component in the frontpart 1 of the motor vehicle which protrudes furthest forward. Theconsequence of this is that when there is a collision with a pedestrian,firstly its lower limb is sensed by the lower lip 21 by means of theregion A marked with a circle. The reinforcement of the lower lip 21with the air guiding part 16 in precisely this region A moves thepedestrian's legs away from the motor vehicle in the direction of travelF so that the pedestrian is deflected about the center of gravity. Whenthere is an impact against the impact foamed part 10, impact forces areabsorbed by the pressing in of the impact foam while the pedestrianrolls over the engine hood in a defined fashion. This virtually rulesout the possibility of the pedestrian with which there has been acollision being run over. For this purpose, the engine hood can beequipped with further measures for protecting pedestrians, for examplean airbag in the region of the upper edge of the engine hood. In furtherembodiments, the lower lip 21 can be embodied so as to be flush with thecontour of the fender covering or positioned slightly behind it.

[0034]FIG. 2 illustrates a longitudinal section through the center ofthe front part 1 of the motor vehicle, identical reference symbolscharacterizing identical components.

[0035] The assemblies which are to be cooled are also apparent from FIG.2, 28 designating a radiator, 29 designating a fan and 30 designatingthe charge air cooler which has already been mentioned in FIG. 1. Incontrast to FIG. 1, a transverse carrier 31 of the bottom supportingstructure can be seen here, said transverse carrier 31 connecting thefront longitudinal carrier sections 3 (not illustrated here) to oneanother.

[0036] Above the transverse carrier 6 which is connected to the impactfoamed part 10, a further cooling air opening 32, which is covered witha radiator grill 33, is provided in the fender covering 5. The air whichflows in through the radiator grill 33 is fed to the radiator 28 locatedbehind it. Above the radiator grill 33 there is an adjoining engine hood34.

[0037] The air guiding part 16 is formed in the shape of a tongue in thecenter of the motor vehicle and thus conducts the air flowing in throughthe cooling air opening 14 directly to the charge air radiator 30. Thetongue-shaped cross section promotes reduction in the air in thedirection of the charge air cooler 30 without unnecessary leak lossesarising due to eddying.

[0038] In order to provide support in the center of the motor vehicle onthe bottom supporting structure, the air guiding part 16 is connected tothe transverse carrier 31. For this purpose, the end 35 which faces thetransverse carrier 31 is embodied in a fork shape. The end 35 which isformed as a fork 36 is partially fitted over the transverse carrier 31and attached to it by means of a screwed connection 37.

[0039] The air guiding part 16 in turn extends from the fork 36 as faras the inner contour 25 of the lower lip 21 which is associated with thefender covering 5 and acts in a reinforcing fashion on the fendercovering 5 when there is a collision with a pedestrian in the region A.The air guiding part 16 has, analogously to FIG. 1, reinforcement ribs26 on its upper side. In order to improve the degree of rigidity,reinforcement ribs 38 are additionally provided on the underside of theair guiding part 16.

[0040]FIG. 3 illustrates a schematic plan view of the air guiding part16 from above, the air guiding part 16 extending in a wing shape overvirtually the entire width of the motor vehicle and beyond the supports39 and 40 (described in FIG. 1) on the front longitudinal carriersection 3.

[0041] Longitudinal section illustrations which have already beendescribed in FIGS. 1 and 2 are shown with lines I—I for FIG. 1, andII-II for FIG. 2.

[0042] As shown FIG. 3, the reinforcement ribs 26 are distributed overthe entire extent of the air guiding part 16 in the transverse directionof the motor vehicle.

[0043] An additional support 41 (illustrated by dot dash lines) isoptionally arranged on the transverse carrier 31 between the supports 39and 40 provided on the longitudinal carrier sections 3, said supportshaving already been described by means of an exemplary embodiment inFIG. 3. Of course, further additional supports 41 may also be providedin order to prevent possibly occurring natural oscillations of the airguiding part 16.

[0044] A further exemplary embodiment of the support 41 on thetransverse carrier 31 is illustrated in FIG. 4 along the line II—II fromFIG. 3.

[0045] The front part 1 of the motor vehicle is constructed analogouslyto the exemplary embodiment illustrated in FIG. 2 and differs only inthe form of the air guiding part 16.

[0046] The air guiding part 16 then extends from the cooling air opening14 over the lower lip 21 as far as the transverse carrier 31 of thebottom supporting structure. In the region of the cooling air opening14, the air guiding part 16 is embodied as a cooling air grill 42 and isattached to opening edges 44 of the cooling air opening 14 by means oflatching projections 43. The air guiding part 16 is of step-shapedconstruction underneath the cooling air opening 14 in order to directthe air which flows in through the cooling air opening 14 in a selectedfashion to the charge air radiator 30. In contrast to the firstexemplary embodiment in FIG. 2, the terminating edge 23 is welded to thelower opening edge 44 of the cooling air opening 14. Alternatively,another means of attachment, for example clipping, may also be provided.The air guiding part 16 bears with a part region 46 against the lowertermination 45 of the lower lip 21 and is also fastened there by meansof welding or clipping.

[0047] The support 41 on the transverse carrier 31 is provided by meansof a screwed connection 47. Alternatively, in the region of the supporton the transverse carrier 31, the air guiding part 16 may be of similarconstruction to the fork 36 in FIG. 2.

[0048] As in the exemplary embodiment in FIG. 2, the air guiding part 16has reinforcement ribs 26 and 38 both on its upper side and on its lowerside. However, in contrast to FIG. 2, the reinforcement ribs 26 and 38are configured with a significantly large area in order to reinforce thelower lip 21 further in the lower region of the fender covering 5. Inparticular, the contour 48 of the reinforcement rib 38 is approximatedto the inner contour 49 of the lower lip 21 so that the cavity 50 whichis formed by the lower lip 21 and the air guiding part 16 is closedvirtually entirely by the reinforcement rib 38. When there is acollision with a pedestrian, there is a strong impact effect as a resultof the reinforced lower lip 21 against the pedestrian's lower leg, andthe pedestrian is thus pushed away from the motor vehicle with the partof his body lying below the center of gravity of his body, and is movedwith the upper part of his body onto the engine hood. At the same time,this promotes the leg region of the pedestrian being moved out of thedanger area of the front wheels.

[0049]FIG. 5 illustrates a third exemplary embodiment of an air guidingpart 16 which is suitable for an elongated front part 1 of a motorvehicle whose front longitudinal carrier sections 3 are arranged abovethe region A which is critical for the impact with a pedestrian.

[0050] In order to support the air guiding part 16 on the longitudinalcarrier sections 3 which are formed as a closed box profile, struts 51are provided which are attached to the underside of each longitudinalcarrier section 3, for example with a welded connection. The struts 51are oriented here, in terms of the vertical axis of the motor vehicle,with their lower end obliquely forward, the orientation of the structs51 being however dependent on the arrangement of the fender system withrespect to their position in relation to the supporting structure 3.

[0051] The lower ends of the structs 51 are connected to one anotherover the width of the motor vehicle by means of a carrier part 52 whichhas a higher degree of degree of rigidity than the air guiding part 16which is composed, for example of plastic. The higher degree of degreeof rigidity of the carrier part may be achieved, for example, byconstructing the carrier part as a closed box profile made of sheetmetal. Given a corresponding configuration of the air guiding part 16,the force which acts when there is an impact with a pedestrian can beabsorbed sufficiently quickly by the air guiding part 16 and passed ontothe bottom supporting structure via the carrier part 52 and the structs51. The air guiding part 16 is set here in such a way that the necessarysupporting force is reached quickly and maintained while values theacceleration and necessary penetration paths for the pedestrian arepreserved.

[0052]FIG. 6 shows the positioning of the air guiding part 16 withrespect to the fender covering 5 and the impact foamed part 10. Thecooling air opening 14 which is partially covered with webs 53 isbounded in its lower region, analogously to the exemplary embodimentsdescribed above according to FIGS. 1 to 4, by the lower lip 21 of thefender unit 2. In contrast to conventional fender units, the fronttermination of the impact foamed part 10 bears with the critical regionA of the lower lip 21 in a virtually vertically extending transverseplane of the motor vehicle. In this way, the lower leg region of apedestrian receives impetus over a large area counter to the directionof travel when there is an impact so that the upper body can roll in adefined fashion in the direction of the engine hood.

[0053] The formation of the air guiding part is illustrated here by wayof example with reinforcement ribs 54 which are arranged on theunderside of the air guiding part 16 over the width of the motorvehicle. As a result, a controlled degree of degree of rigidity isobtained over the entire width of the motor vehicle, preventing thelower leg region penetrating or rotating too far into the lower lip 21.The air guiding part 16 can be supported on the inner contour 24 of thelower lip 21 by means of appropriate connecting technology such asscrews, bonding, rivets, in order to achieve effective force support.

[0054] The degree of rigidity of the air guiding part 16 can beindividually matched by means of the following factors to the necessaryforce/displacement characteristic which is specific to the motor vehicleand fender:

[0055] type of material, material thickness and material geometry;

[0056] position, size, embodiment and wall thickness of thereinforcement ribs;

[0057] alternative use of net-shaped or honeycomb-shaped reinforcementstructures;

[0058] the degree of rigidity of the carrier part 52 is preferablyhigher than that of the air guiding part 16 (alternatively, the carrierpart 52 can be matched to the air guiding part 16 in such a way thatjoint deformation of both parts is possible);

[0059] connecting technologies between the lower lip 21 and a guidingpart 16

[0060] position and design of the reinforcement ribs 54 over the widthof the motor vehicle.

[0061] Irrespective of the aforesaid factor for matching theforce/displacement characteristic, the air guiding part 16 isconstructed in such a way that an approximately identical deformationbehavior, and thus identical kinematics of the impact of the leg, can beensured over the entire width of the motor vehicle.

1. A front part of a motor vehicle having a bumper unit which comprisesan air guiding part which is arranged underneath the fender, a fendercovering and a front fender which is covered on the outside by thefender covering and which can be connected in its lower region to abottom supporting structure of the motor vehicle, characterized in that,in the event of a head-on impact, the air guiding part (16) interactswith the fender covering (5) and stiffens it in a region which ispositioned in front of the fender (4), it being possible to support theair guiding part on the bottom supporting structure (3, 31).
 2. Thefront part of a motor vehicle as claimed in claim 1, characterized inthat the air guiding part (16) which is arranged underneath a coolingair opening (14) which is introduced into the fender covering (5)extends over virtually the entire width of the motor vehicle.
 3. Thefront part of a motor vehicle as claimed in claim 1, characterized inthat the air guiding part (16) is supported at the front end (18) by twolongitudinal carrier sections (3) which are associated with the bottomsupporting structure.
 4. The front part of a motor vehicle as claimed inclaim 2, characterized in that a rear end collision protection element(17) which is connected to the air guiding part (16) is fitted over eachof the front ends (18) of the longitudinal carrier sections (3).
 5. Thefront part of a motor vehicle as claimed in claim 4, characterized inthat the air guiding part (16) is constructed as one piece with the rearend collision protection element (17) as a plastic part.
 6. The frontpart of a motor vehicle as claimed in claim 3, characterized in that theair guiding part (16) extends laterally beyond the supports (39, 40) onthe longitudinal carrier sections (3).
 7. The front part of a motorvehicle as claimed in claim 1, characterized in that the contour (23) ofthe air guiding part (16) which faces the fender covering (5) is adaptedto the internal contour (23) of the fender covering (5), the contour(24) of the air guiding part (16) bearing against and being connected tothe internal contour (24) of the fender covering (5).
 8. The front partof a motor vehicle as claimed in claim 7, characterized in that the airguiding part (16) is embodied in one piece with the fender covering (5).9. The front part of a motor vehicle as claimed in claim 7,characterized in that the air guiding part (16) has a wing-like shape, anumber of reinforcement ribs (26) which are oriented in the longitudinaldirection of the motor vehicle and are spaced apart from one another inthe transverse direction of the motor vehicle being arranged on theupper side of the wing.
 10. The front part of a motor vehicle as claimedin claim 9, characterized in that reinforcement ribs (38) are arrangedon the underside of the wing, the contour (48) of said reinforcementribs (38) which lies opposite the fender covering (5) being matched tothe internal contour (49) of the fender covering (5).
 11. The front partof a motor vehicle as claimed in claim 9, characterized in that the wing(16) forms a closed hollow section together with the region (21) of thefender covering (5) which is positioned in front of it.
 12. The frontpart of a motor vehicle as claimed in claim 3, characterized in that, inaddition to support (39, 40) being provided on both sides at the frontends (18) of the longitudinal carrier sections (3), support (41) isprovided on a transverse carrier 31, which connects the frontlongitudinal carrier sections (3).